Prosthetic knee appliances have evolved over the past decades into highly complex technical components. The evolution of prosthetic knee systems has resulted in numerous choices being available to patients, doctors, and prosthetists. The use of almost any prosthetic knee system requires that patients learn and develop skills to control the motion of the joint so that they can walk, stand, sit, and generally maintain stability. Therefore, when selecting a prosthetic knee system, a variety of factors must be considered, such as the patient's age, health, activity level, and lifestyle.
The use of prosthetic knee systems by very young children can be particularly problematic. Never more so than with infants and children who have not yet learned to walk. Traditionally, infants and pre-ambulatory children who have undergone trans-femoral (above-knee) or knee-disarticulation (at the knee) amputation are initially fitted with pediatric straight leg prostheses. This ensures knee stability in early “cruising” (walking sideways while holding onto furniture or other supports) and walking stages. However, straight-leg prostheses can dramatically inhibit normal crawling and other movements in these young patients.
The use of an articulated or “free-knee” prosthetic eases crawling and allows for normal body positioning and movement while sitting. For children learning to walk, a free-knee prosthetic also aids in the initial step of pulling to a standing position. But, ambulation requires a stabile knee. In order for a traditional free-knee prosthetic to remain straight during weight bearing, the center of mass must be in front of the knee or there must be hip extensor movement keeping the knee locked. This is a learned skill that cannot be expected of a child just learning to walk. Inevitably, as a child takes his or her first steps and transfers weight to the prosthesis, the center of mass collapses behind the axis of the free-knee joint causing the child to fall.
Despite advances in prosthetic knee devices, there still exists a need for a pediatric prosthetic knee system that provides the advantages of free-knee movement and the security of a straight knee for standing and ambulation. Such a prosthetic knee system would aid in the proper movement and development of pre-ambulatory pediatric patients.